1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming process controlling method to form an image on a sheet by permanent color toner and decolorizing toner to be decolorized.
2. Description of the Related Art
In Japanese Patent Application Publication No. 11-212338, the image forming art applied to an image forming apparatus of an intermediate transfer system is disclosed. In the image forming apparatus, by a rotary developing device, on a photosensitive drum, four colors of yellow (Y), magenta (M), cyan (C), and black (K) are developed one by one, thus a toner image is formed. The toner image obtained by forming the colors on the photosensitive drum one by one like this is transferred onto an intermediate transfer belt at a primary transfer position.
Thereafter, the photosensitive drum and intermediate transfer belt timely make 4 revolutions, thus a toner transfer image of full color of 4 superimposed colors is formed on the intermediate transfer belt and the toner transfer image is secondarily transferred onto a transfer sheet which is a recording medium by a secondary transfer unit. The transfer sheet on which the superimposed toner image is transferred secondarily is fixed by a fixing unit and then is externally taken out.
Conventionally, as a product using decolorizing toner, an image forming apparatus using a constitution that a black developing unit of a monochromatic printer or a monochromatic MFP is replaced with decolorizing toner is commercialized. However, it is an exclusive device, so that when copying a use not suited to use decolorizing toner (printing a document requiring long-term preservation, etc.), another printer or MFP capable of printing by permanent color toner must be used.
A sheet which is subject to the decolorizing process after forming an image by decolorizing toner is hardly distinguished from a new sheet at a glance. When forming an image on such a sheet regenerated after the decolorizing process by permanent color toner like this, the concerned sheet cannot be reused by the image forming process by decolorizing toner.